The Study on the Mechanism of Ischemic Preconditioning of the Myocardium

ATP-sensitive K channel have been reported to play a major role in ischemic preconditioning。当前的研究被设计为clarify the effect of mitochon？al K2 ATP D2 channel opener on the hypoxia-reperfusion injury。Ventricular Myocytes从Sprague-Dawley大鼠被研究过。Cardiomyocytes被超充用无氧化葡萄糖轮胎解决方案，它在阳性压力下平衡了99.99%的氮素，15分钟后被40分钟的正常氧化轮胎解决方案覆盖。Diazoxide （30？M）、a specific mitochon？al K2 ATP D2 channel opener was administered to the diazoxide group （D group） 5 minutes prior to anoxic perfusion until the end of anoxic perfusion。通过BCECF测量的内部pH值和通过显微荧光测量系统ARGUS 200记录的myocytes形状（Hamamatsu Photonics， Hamamatsu， Japan）。罗德形状的细胞被认为是活的。与对照组相比，D组中氧化还原灌注末端的心脏细胞活力明显高于D组（59.3±10.6对22.0± 13.3%; n=8，6大鼠; <0.05）。Myocytes的pH值在两组之间是相似的，在氧化物灌注的末端。控制组显示的圆形细胞中大多数杀伤细胞，但D组显示的刚性接触中杀伤细胞的一半（控制组：圆形细胞62.3%，刚性接触10.7%; D组：圆形细胞20.3%，刚性接触19.5%）。当分离的心细胞被肥皂泡制成皮肤后洗涤含有EGTA的溶液，并在ATP依赖的溶液中挂起， myocytes成为rigor Contracture。在anoxia-reoxygenation injury of the isolated cardiomyocyte of rat without any change of intracellular pH。此protective effect might be due to reducing Ca overload during anoxia-reoxygenation perfusion。

ATP-sensitive K channel (KィイD2ATPィエD2 channel) have been reported to play a major role in ischemic preconditioning. The present study was designed to clarify the effect of mitochondrial KィイD2ATPィエD2 channel opener on the hypoxia-reperfusion injury. Ventricular myocytes isolated from Sprague-Dawley rat were studied. Cardiomyocytes were superfused with anoxic glucose-free Tyrode solution, which was equilibrated with 99.99% nitrogen under positive pressure, for 15 minutes followed by normoxic Tyrode solution for 40 minutes. Diazoxide (30 μM), a specific mitochondrial KィイD2ATPィエD2 channel opener was administered to the diazoxide group (D group) 5 minutes prior to anoxic perfusion until the end of anoxic perfusion. Intracellular pH measured by BCECF and the shape of myocytes were recorded by microscopic fluorometric system ARGUS 200 (Hamamatsu Photonics, Hamamatsu, Japan). Rod-shaped cell was considered to be alive. The viability of cardiomyocytes at the end of anoxia-reoxygenation perfusion was significantly higher in D group compared with control group (59.3±10.6 vs 22.0±13.3% ; n=8,6 rats ; <0.05). The pH of myocytes was similar between two groups at the end of anoxic perfusion. Most of the killed cells of the control group showed round cells but the half of the killed cell of D group showed rigor contracture (control group : round cells 62.3%, rigor contracture 10.7% ; D group : round cells 20.3%, rigor contracture 19.5%). When isolated cardiomyocytes were made skinned by saponin after washing by EGTA-containing solution, and suspended in ATP-depleted solution, myocytes became rigor contracture. Mitochondrial KィイD2ATPィエD2 channel opener showed the protective effect on the anoxia-reoxygenation injury of the isolated cardiomyocyte of rat without any change of intracellular pH. This protective effect might be due to reducing Ca overload during anoxia-reoxygenation perfusion.